Compression-compatible digital watermark algorithm for authenticity verification and localization

In this paper, a new fragile watermarking system for authenticity verification is presented. This technique can detect and locate minor changes in a marked image. The method can be implemented in any domain. The embedding procedure modifies the representative value of a selected vector of coefficients according to the embedded watermark bit value. The mapping of the bits to the representative values and the formation of the orthogonal vectors are secured using a symmetric key system. The detector is a standalone system that does not need any prior knowledge about the original image or the embedded watermark. A tolerance bandwidth can be set to a minimum to reduce the level of false negative detector responses. Assuming there is a consistent pattern of tampering, an optimization algorithm has been designed to further reduce the false negative probability. By embedding the watermark in the same domain as is used for compression, the system can allow compression as an undetectable content preserving operation if the amount of quantization is known in advance. Experimental results of this system embedded in the DCT and wavelet domain illustrate the performance and effectiveness compared with other reported fragile watermarking methods